Plastic hinge length of FRP strengthened reinforced concrete columns subjected to both far-fault and near-fault ground motions

In a strong earthquake, an RC column develops plastic deformations in regions often defined as plastic hinge regions. The formation of a plastic hinge in an RC column in these regions depends on the characteristics of the earthquakes as well as on the column details. Recordings from recent earthquakes have demonstrated that ground motions in near field to a rupturing fault can contain a large energy. This energy can cause considerable damage during an earthquake. Therefore, many recently designed and constructed buildings may require strengthening in order to perform well when subjected to near-fault earthquakes. Fiber Reinforced Polymers are considered to be a viable strengthening method due to their relatively easy and quick installation. In this paper, 1350 inelastic time-history analyses have been performed to predict the nonlinear behavior of FRP strengthened RC columns under both far-fault and near-fault earthquakes. The effects of axial load, height-depth ratio and the amount of longitudinal reinforcement, as well as different characteristics of earthquakes, are evaluated and the results are compared with the corresponding experimental data. Based on the results, simple expressions are proposed that can be used to estimate plastic hinge length of FRP strengthened RC columns subjected to both far- and near-fault earthquakes.